1. Field of the invention
This invention relates generally to fans suitable for use in a humid atmosphere, and more particularly to such a fan provided in an evaporator compartment of a refrigerator for circulating a cooling air through storage compartments.
2. Description of the prior art
A fan has conventionally been provided in an evaporator compartment of a household refrigerator for circulating a cooling air through storage compartments. FIG. 12 illustrates one of such conventional fans. An evaporator 2 is provided in the lower interior of an evaporator compartment 1. A fan 3 is provided over the evaporator 2 in the evaporator compartment 1. The fan 3 comprises an electric motor 4, an impeller 6 mounted on a rotational shaft 5 of the motor 4, a bell-mouthed fan casing 7 surrounding the impeller 6.
A temperature around the fan 3 ranges between -20 and -30.degree. C. while the evaporator 2 is in operation for cooling. On the other hand, the temperature around the fan 3 ranges between +10 and +20.degree. C. while a heater (not shown) is turned on to apply heat to the evaporator 2 so that the same is defrosted. Thus, the temperature around the fan 3 rises during the defrosting operation and accordingly, a dew condensation tends to occur around the fan 3. In view of this, an inner rotor type motor is usually employed as the motor 4. A main body of the motor 4 except the shaft 5 is covered with a motor cover 8 so that water is prevented from penetrating the inside of the motor 4. However, the inner rotor type motor is disadvantageous in that an axial dimension thereof is increased.
To overcome the above-described disadvantage, the prior art has proposed employment of an outer rotor type motor as the fan motor. In this case, the impeller is provided integrally on the outer periphery of a rotor yoke of a rotor. In the outer rotor type motor, the axial dimension thereof can be rendered smaller than in the inner rotor type motor 4. However, in the fan comprising the outer rotor type motor and the impeller provided on the outer periphery of the rotor yoke, the overall motor cannot be covered with a cover from the point of view of its structure. As a result, water tends to penetrate the inside of the motor. In particular, a gap between the rotor and the stator of the motor cannot be avoided such that water penetrates the inside of the motor through the gap. In this case, the stator, which is a principal electrical component of the motor, may be covered with a molded layer molded from a synthetic resin so that water can be prevented from penetrating the inside of the motor, but yet it is desirable to prevent water from penetrating the overall inside of the motor.